bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

use an enum in matches_projection_projection

Browse source
This commit is contained in:
Michael Goulet 2022-02-12 13:30:30 -08:00
parent 784c7a6cad
commit 879e4f8131
2 changed files with 28 additions and 16 deletions
Download patch file Download diff file Expand all files Collapse all files

7
compiler/rustc_trait_selection/src/traits/project.rs
View file

@ -19,6 +19,7 @@ use super::{Normalized, NormalizedTy, ProjectionCacheEntry, ProjectionCacheKey};
use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
use crate::infer::{InferCtxt, InferOk, LateBoundRegionConversionTime};
use crate::traits::error_reporting::InferCtxtExt as _;
use crate::traits::select::ProjectionMatchesProjection;
use rustc_data_structures::sso::SsoHashSet;
use rustc_data_structures::stack::ensure_sufficient_stack;
use rustc_errors::ErrorReported;
@ -1248,7 +1249,7 @@ fn assemble_candidates_from_predicates<'cx, 'tcx>(
});
match is_match {
Some(true) => {
ProjectionMatchesProjection::Yes => {
candidate_set.push_candidate(ctor(data));
if potentially_unnormalized_candidates
@ -1260,10 +1261,10 @@ fn assemble_candidates_from_predicates<'cx, 'tcx>(
return;
}
}
Some(false) => {}
None => {
ProjectionMatchesProjection::Ambiguous => {
candidate_set.mark_ambiguous();
}
ProjectionMatchesProjection::No => {}
}
}
}

37
compiler/rustc_trait_selection/src/traits/select/mod.rs
View file

@ -1508,15 +1508,18 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
})
}
/// Return Some(true) if the obligation's predicate type applies to the env_predicate, and
/// Some(false) if it does not. Returns None in the case that the projection type is a GAT,
/// Return `Yes` if the obligation's predicate type applies to the env_predicate, and
/// `No` if it does not. Return `Ambiguous` in the case that the projection type is a GAT,
/// and applying this env_predicate constrains any of the obligation's GAT substitutions.
///
/// This behavior is a somewhat of a hack to prevent overconstraining inference variables
/// in cases like #91762.
pub(super) fn match_projection_projections(
&mut self,
obligation: &ProjectionTyObligation<'tcx>,
env_predicate: PolyProjectionPredicate<'tcx>,
potentially_unnormalized_candidates: bool,
) -> Option<bool> {
) -> ProjectionMatchesProjection {
let mut nested_obligations = Vec::new();
let (infer_predicate, _) = self.infcx.replace_bound_vars_with_fresh_vars(
obligation.cause.span,
@ -1553,20 +1556,22 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
if is_match {
let generics = self.tcx().generics_of(obligation.predicate.item_def_id);
if !generics.params.is_empty() {
// If any of the obligation's predicate substs shallow-resolve to
// something new, that means that we must have newly inferred something
// about the GAT. We should give up with ambiguity in that case.
if obligation.predicate.substs[generics.parent_count..]
// FIXME(generic-associated-types): Addresses aggressive inference in #92917.
// If this type is a GAT, and of the GAT substs resolve to something new,
// that means that we must have newly inferred something about the GAT.
// We should give up in that case.
if !generics.params.is_empty()
&& obligation.predicate.substs[generics.parent_count..]
.iter()
.any(|&p| p.has_infer_types_or_consts() && self.infcx.shallow_resolve(p) != p)
{
return None;
}
{
ProjectionMatchesProjection::Ambiguous
} else {
ProjectionMatchesProjection::Yes
}
} else {
ProjectionMatchesProjection::No
}
Some(is_match)
}
///////////////////////////////////////////////////////////////////////////
@ -2766,3 +2771,9 @@ impl<'o, 'tcx> fmt::Debug for TraitObligationStack<'o, 'tcx> {
write!(f, "TraitObligationStack({:?})", self.obligation)
}
}
pub enum ProjectionMatchesProjection {
Yes,
Ambiguous,
No,
}